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Types of Bacteria

Label each of the pictures below as either:

Cocci Bacilli and/or Spirilla

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Definition of bacteria

Diagram of A bacterial Cell

Diagram of the three different types of bacteria

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Structure and Function of a bacterial cell

Structure Function

Cell Wall

Cell Membrane

Cytoplasm

Nuclear Material (DNA, RNA, Chromosomes)

Flagella

Differences between bacteria and animal and Plants Cells

Bacteria Animal Plant

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Bacteria reproduce simply by dividing in two in a process called binary fission. The daughter cells produced are genetically identical to the parent cells unless a mutation occurs when the DNA is being copied. wo identical DNA molecules migrate to opposite ends of the cell as a transverse wall forms, dividing the cell in two. The cells can now separate and enlarge to original size. Under ideal conditions, a bacterium can undergo binary fission every 10-20 minutes producing over 1030 progeny in a day and a half. If sources are unlimited, exponential growth would be expected.

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Conditions that encourage the of Reproduction in Bacteria

Conditions Effect on bacterial rate of reproductionNutrients/ available

food supply

Oxygen

pH

Moisture Conditions

Temperature

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Growth Rate of different species of bacteria

The time interval required for a bacterial cell to divide or for a population of bacterial cells to double is called the generation time. Generation times for bacterial species growing in nature may be as short as 15 minutes or as long as several days.

Generation times for some common bacteria under optimal conditions of growth.

Bacterium Medium Generation Time (minutes)

Escherichia coli Glucose-salts 17Bacillus  megaterium Sucrose-salts 25Streptococcus lactis Milk 26Streptococcus lactis Lactose broth 48Staphylococcus aureus Heart infusion broth 27-30Lactobacillus acidophilus Milk 66-87

Rhizobium japonicum Mannitol-salts-yeast extract 344-461

Mycobacterium tuberculosis Synthetic 792-932

Treponema pallidum Rabbit testes 1980

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Bacterial Reproduction Rates

A typical bacterium, Like E. Coli can reproduce at amazing rates. For examples, many divide at a rate of once every 20 minutes. Using this as an example, complete the table below to show how many bacteria you would have after 12 hours. Use the graph paper on the following page to plot this information

Time (Minutes) Number of Bacteria

Time (Minutes) Number of Bacteria

0 1 380

20 2 400

40 4 420 (7 hours)

60 (1 hour) 8 440

80 460

100 480 (8 hours)

120 (2 hours) 500

140 520

160 540 (9 hours)

180 (3 hours) 560

200 580

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220 600 (10 hours)

240 (4 hours) 620

260 640

280 660(11 hours)

300 (5 hours) 680

320 700

340 720 (12 hours)

360 (6 hours)

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Pasture’s Experiment

http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html

In the 1800’s, the great French scientist Louis Pasture testes the validity of a widely held belief in spontaneous generation. Or centuries, the general population and naturalists alike believed that a variety of organisms could arise spontaneously, without being generated from similar organisms.

Louis pasture was not the first to conduct experiments on spontaneous generation. For examples, two centuries earlier, in 1668, an Italian physician named Francesco Redi showed that maggots do not emerge from rotting meat by spontaneous generation, but instead develop from eggs laid by flies. Although Redi’s experiment was convincing, most people applies its conclusions only to certain organisms. By Pasteur’s time, for examples, naturalists generally rejects spontaneous generation when it came to macroscopic life, such as insects and molluscs, but help on to the notion when in applied to microscopic life, such as bacteria.

In 1862, Pasteur set up an experiment to refute the notion of spontaneous generation for microscopic life. He based his experimental design on a number of observations. He knew that bacteria grow in open containers of meat broth. He also knew that if the broth is boiled for an hour in a sealed container that remains sealed, no bacteria will grow in it. Additionally he observes that bacteria are found in dust particles that float in the air. Armed with this information, Pasture set up a definitive experiment to test whether microbes arise from pre-existing microbes or are generated spontaneously.

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Koch’s Postulates

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Penicillium notatum

Gather information about the discovery and the identification of penicillin from the fungus Penicillium notatum. In the boxs below summarise your research and then present in a 1000 word essay titled

‘Identifying penicillin as an antibiotic.’ Make sure you focus your essay on the circumstances surrounding the identification of penicillins properties rather than on the life histories of the men involved. You may include diagrams in your essay where appropriate.

Louis Pasture

Joseph Lister

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Alexander Flemming

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Howard Florey

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How Penicillium works

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Other Types of Antibiotics

Name of Antibiotic Source Mode of Action Bacteria that they effect

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plan, choose equipment and resources for, analyse the risk, implement appropriate procedures for and perform a first-hand investigation to culture bacteria present in our surroundings and relate the growth rate to environmental conditions of temperature

Experiment: Bacteria and their growth rate

Aim: To culture bacteria at different temperatures and compare their growth rate

Hypothesis: If bacteria are grown at 30° C and 4 °C then ..........................................................

………………………………………………………………………………………………………………………………………………..

Equipment:

agar plates Incubator x 2 Known samples of:

oo o o

Inoculating loop Gloves Para film to seal agar plates Bunsen burner Matches Permanent Marker

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Risk Assessment:

Risk Prevention JustificationSpores released from agar plates could be breathed in

Agar plates are sealed and never reopened

Bacteria multiply rapidly and can mutate into forms of bacteria harmful or even deadly. The bacteria that grown may be resistant to antibiotics.

Growing unknown cultures that are potentially harmful

Sterilise the tools, lab bench and hands before inoculating agar plate

Do not expose the agar late to the air unnecessary amount of time

Do not incubate the plates at human body temperature (37 C)

Never reopen the plates

Dispose of the plates correctly

Method:

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Results:

Growth rate of different species of bacteria incubated at different temperatures

Number of Cultures/Day

Plate

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1. Compare the growth rate of bacteria at different temperatures in general (2M)

2. In general, did you see any identifiable differences in the growth rate of different species of bacteria? Explain these observations using your research(2M)

3. Identify the risks associated with culturing bacteria and outline how these risks can be eliminated or reduced. (4M)

4. Outline how you carried out an investigation to determine the effect of temperature on the rate of reproduction of bacteria. (5M)

5. Identify the dependent and independent variables in the investigation you carried out to determine the effect of temperature on the rate of reproduction of bacteria. (2M)

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6. Explain how the reliability and validity of your experiment could be improved upon (4M)

7. Write a hypothesis and a matching conclusion related to your investigation carried out to determine the effect of temperature on the rate of reproduction of bacteria. (2M)

8. Propose how the investigation you carried out applies the processes that scientists use to test and validate scientific ideas (such as models, theories or laws). (4M)

9. Identify three factors that determine the rate of reproduction of bacteria and explain the effect of each. (6M)

10. Outline the role of “good bacteria” on the skin in inhibiting the reproduction of disease-causing bacteria on the skin. (4M)

11. From your research, what general conclusions did you reach about the rate of reproduction of different bacteria? (3M)

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12. Write a conclusion (1M)

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The Problem with Penicillin

Read ‘The problem with Penicillin’ on page 213 of Spotlight Senior Science, write a summary of the information and answer the following questions.

Summary

1. Suggest reasons why a person may require two different types of antibiotic to a fight a particular infection

2. Propose reasons why a combination of antibiotics with penicillin followed by erythromycin might be used to treat a particularly difficult or reoccurring infection

3. List the names of 10 different types of antibiotics

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Read March of the Superbugs in Spotlight Senior Science Pages 214-125 and questions 1-7 on page 215

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